Detecting Change Using Standard Global Perimetric Indices in Glaucoma.

Abstract

Various global indices are available to summarize results from standard automated perimetry. This study asks which index can detect significant deterioration earliest, for a fixed specificity. Comparison of prognostic indices. Two cohorts were tested. A test-retest cohort contained 5 reliable visual fields, within a short interval, from 45 eyes of 23 participants with glaucoma and/or likelihood of developing glaucoma. A separate longitudinal cohort contained 508 eyes from 330 participants, tested on average 13 times. Three global indices were extracted: mean deviation (MD), pattern standard deviation (PSD), and visual field index (VFI). For each index we defined a critical P value Crit_Index, such that 5% of test-retest series showed significant deterioration with P < Crit_Index, using artificial "test dates" in random order. Therefore these criteria have 95% specificity over series of 5 tests. The times to detect significant deterioration in the longitudinal cohort were compared using a survival analysis model. The median time to detect significant deterioration with MD was 7.3 years (95% confidence interval [CI] 6.8-7.9 years). For VFI, the median was 8.5 years (95% CI 7.9-9.0 years); this comparison had P = .088. For PSD, the median was 10.5 years (95% CI 9.3-11.7 years), slower than MD with P < .001. Within the first 5 years of a series, MD detected significant deterioration in 138 eyes, vs 104 for VFI (P = .0013) and 107 for PSD (P = .029). MD detected significant deterioration sooner than VFI or PSD. In particular, MD detected more eyes in the first 5 years of their follow-up, which were presumably undergoing more rapid progression.